Fei Xiong and her eight-year-old son looked at each other and sensed something was wrong as Asiana Flight 214 came in low over San Francisco Bay.

"My son told me: 'The plane will fall down, it's too close to the sea.' I told him: 'No, baby, it's OK, we'll be fine.' And then the plane just fell down," Xiong said on Sunday, wearing a plastic brace on her injured neck.

Within moments, the aircraft was hurtling out of control, its rear section ripped off. Baggage was tumbling from the overhead bins on to passengers and oxygen masks dropped down as dust filled the plane. People all around her were screaming, she said.

The crash on Saturday at San Francisco airport killed two teenage girls from China, whose bodies were found outside the wreckage, and injured dozens of others. At least two others suffered paralysing back injuries, hospital officials said.

Xiong, from China, was sitting in the middle of the plane when she felt the strong jolt and her neck was violently flung back and forth.

After the plane came to a rest, she grabbed her son and headed for the nearest door, which was open. She said the emergency chute had not deployed so they jumped to the tarmac.

In the first comments by a crew member, cabin manager Lee Yoon-hye told reporters that when the captain ordered an evacuation, she knew what she had to do.

"At that point, my head became clear," she said on Sunday night at a San Francisco news conference. "I was only thinking about rescuing the next passenger."

Lee said she was calm despite the flames. "I didn't have a moment to feel that this fire was going to hurt me," she said.

When a teenage boy was afraid to jump on to the inflatable slide, Lee said a flight attendant carried him on her back and they slid down together.

"The kid said he was scared. My colleague carried him on her back and jumped. I was inside the plane. [My colleague] was crying as parents tearfully hugged their kid after evacuating safely," Lee said.

She also said passengers remained calm during the evacuation.

In seat 40C, near the rear of the aircraft, Wen Zhang said she thought the landing gear had failed when she felt the tail slam against the ground. She, too, was with her young son, aged four.

"I had no time to be scared," she said. Zhang, who was unhurt, picked up her child, who had hit the seat in front of him and broke his left leg. She could see a hole that ripped open at the back of the jumbo jet where the bathroom had been and carried her son to safety.

"It left a hole very close to my seat," she said. "Enough for two persons to get out."

Sitting near Zhang was 39-year-old Shi Da, who was travelling with his wife and teenage son. He was shocked by the violent shaking of the crash, then the realisation that the back of the plane had ripped off. He stood up and could see the tail, but the kitchen was missing with nothing but a hole.

"I can see through the hole to the runway and the ground," Da said. "So we just grabbed our bags and rushed out from the tail, from the hole."

The passengers who made it out alive sat on the tarmac for half an hour waiting for buses and watching the aircraft go up in flames as firefighters hosed it down. Ambulances took the badly injured away, but 123 people walked away mostly unhurt.

Many did not have their passports, cellphones or money.

Most survivors suffered minor injuries, and were just starting to realise how close they'd come to death.